It would be helpful if you gave us some detail on your year and model MH. In the meantime, here's some info based on my experience with my 2002 Suncruiser 35U.
1. It's not necessary to remove the carpet that's still under the slide when it's extended. If you hit the retract button slightly, the inboard edge of your slide should lift enough for you to cut the carpet with a utility knife far back enough so it's not visible after installing your new flooring. If you have difficulty, try retracting it an inch or so on top of two or three small wedges, no more than 3/8", or so, high.
2. The slide should work properly, especially if your new floor has some thickness to it as opposed to sheet vinyl.
3. If you install laminate or plank vinyl, you may have a problem with scratching from sand or grit. This means your floor has to be very clean before retracting. There are also floor protectors that you can buy or make to lay down before retracting.
https://www.amazon.com/AP-Products-0.../dp/B0031NFUHQ
4. I'm not sure what it's called but your existing slide probably has a plastic fitting running under it's inboard edge to slide over the carpet. This can be replaced with a carpeted fitting to run over hard flooring. I didn't do this so I can't tell you how to do it.
5. The reason I didn't do #4 is that I replaced my carpet with commercial quality, 19" or 20" carpet tiles. They're a nice compromise between hard flooring and your old carpet. They're nice on bare feet, stain resistant, easy to keep clean, don't scratch and easy to install. I installed mine with double-sided carpet tape. If one gets damaged it's easy to replace (buy extra).